This invention relates to low-frequency transmitting and receiving antennas, and more particularly, to a highly portable, easily erectable transmitting and receiving antenna for the high frequency bands.
There have been proposed and utilized many vertically polarized antennas for use in the high frequency (HF) bands, such as nominally 1.8 to 30 MHz. Perhaps the best known such antenna is the quarter-wave ground plane monopole wherein the radiating element is electrically substantially 1/4 wavelength. Various multi-band variations of this antenna have been proposed, both with and without radial elements at the base of the antenna for establishing a ground plane, and utilizing one or more capacitive-inductive (LC) traps along the length of the radiating element to provide resonance at the desired center frequencies within the bands of interest thereby controlling the electrical length of the antenna for the different bands.
In another well-known multi-band antenna arrangement, the vertical element is one-half of the desired maximum wavelength, and is end-fed at the bottom of the element through an adjustable matching network, with traps provided along the length for causing the antenna to provide shorter effective lengths at higher frequencies within the bands of interest. In the design of such prior antennas, the capability of providing all-band operation within the frequency range desired involves, at best, a compromise in design. The use of LC traps along the length degrades efficiency and brings about the need, when changing frequency, for readjusting the matching network which, because of its typical complexity (which may include servomotors for inductive tuning from a remote location) is bulky and is not amenable to being integrated into the design of the antenna itself.
In any event, the use of bulky, cumbersome traps and extrinsic matching networks causes the resultant antenna to be anything but portable and anything but easily erected. Typically, such antennas of the prior art have therefore been intended for permanent or semi-permanent installation.
It is desirable to provide an HF antenna which is not only portable but which can be quickly and easily deployed and, thus, erected for immediate usage in a variety of areas of utilization, such as, for example, for military contingency communications, for emergency usage as by amateur radio and civil defense operators, for amateur radio portable operations, for short wave listening, and others who must have the capability for interim communications or do not have the facility for a permanent antenna.
Accordingly, among the several objects of the invention may be noted the provision of a highly portable transmitting and receiving antenna for the HF bands, as substantially from 1.8 to 30 MHz; the provision of such an antenna which is also quickly and easily deployed, and easily redeployed; which can be used in restricted spaces; which is utilizable for various modes of transmission, including AM, SSB and FM, and for radiotelephony, radiotelegraphy and facsimile, in any of a wide variety of usages, including emergency communications generally, for amateur radio, civil defense, military and contingency communications, as well as for portable and standby purposes generally; which is superlative for both receiving and transmitting throughout the entire HF frequency spectrum.
Among other objects of the invention may be noted the provision of such an antenna which when transmitting provides an excellent electrical impedence match at the desired frequency with a wide variety of transmitting equipment, including even solid state designs which are highly intolerant of electrical mismatch; which provides an extremely low voltage standing wave ratio (v.s.w.r.) for allowing the efficient transfer of transmitted energy to the antenna without substantial energy being reflected from the antenna along the transmission line to the transmitter; which functions well throughout the entire HF band; which obviates the need for the customary earth-ground connection; which functions electrically as a complete vertical half-wave radiator for providing an enhanced radiation pattern with gain typical of pure half-wave dipoles, such as typically at least 2.15 db over an isotropic radiator; which is asymmetrically fed at an advantageous location along its length; which includes an integral matching network of compact, easily-adjusted congifuration for radiation by the antenna within broad non-critical bands of interest within the HF spectrum, and which matching network also is coaxially configured with respect to the antenna for permitting the antenna elements and matching network to telescope; and which does not require that the matching network be readjusted when frequency is changed within a given band for which the matching network has been set, demonstrating wide band impedance matching.
Among still other objects by the invention may be noted the provision of such an antenna of which provides an extremely compact highly portable unit when collapsed; which when collapsed forms a completely self-contained package without requiring separate packaging provision for the various elements of the antenna; which can be quickly and easily as well as safely erected by a single person; which can be utilized in many different locations and orientations; which is easily manufactured, lightweight and easily shippable or transportable, such as by hand or as airline carry-on baggage, for example.
Other objects will be in part apparent and in part pointed out hereinbelow.